Sensors for monitoring the condition of a fetus, especially electrically conductive sensors of the intrusive or skin-penetrating type, have been proposed heretofore to enable the condition of the fetus to be monitored during the birth process, especially by monitoring the electrocardiagram of the fetus.
In general, the prior art electrodes for this purpose have not proved to be fully satisfactory because of a lack of reliability of the electrode, i.e. the sensor, the inability to diagnose adequately, from the data obtained, a developing or existing condition warranting immediate attention, and other reasons which derive from the means in which the sensor or electrode is applied.
Birth-monitoring systems of the conventional type can generally be considered in three categories. A first monitors the fetus electrocardiographically. A second measures extra-uterine and/or intra-uterine pressure fluctuations, especially the strength of labor contractions. The third analyzes the oxygen partial pressure or pH values of the blood, either by direct sampling of the fetal blood at the scalp of the fetus or by sensors which are fixed to the scalp.
All of these approaches have disadvantages, and a common disadvantage of all of them is that they are not fully capable of indicating danger to the fetus so that frequently, as a result of ambiguity in the measurements, the birth is concluded prematurely with the use of forceps and other instruments which may endanger the child or the mother. Sometimes, because of ambiguities in the results, a caesarean section is unnecessarily performed.